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Radiocarbon Data Reveal Contrasting Sources for Carbon Fractions in Thermokarst Lakes and Rivers of Eastern Canada (Nunavik, Quebec)
Author(s) -
Gonzalez Moguel Regina,
Bass Adrian M.,
Garnett Mark H.,
Pilote Martin,
Keenan Benjamin,
Matveev Alex,
Douglas Peter M. J.
Publication year - 2021
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
eISSN - 2169-8961
pISSN - 2169-8953
DOI - 10.1029/2020jg005938
Subject(s) - permafrost , thermokarst , peat , dissolved organic carbon , radiocarbon dating , environmental science , total organic carbon , hydrology (agriculture) , carbon fibers , carbon cycle , environmental chemistry , geology , oceanography , ecology , ecosystem , chemistry , paleontology , materials science , geotechnical engineering , composite number , composite material , biology
Greenhouse gas emissions from permafrost organic carbon decomposition in lakes and rivers can accelerate global warming. We used radiocarbon ( 14 C) measurements to determine the predominant sources of dissolved organic carbon (DOC), particulate organic carbon (POC), dissolved inorganic carbon (DIC), and methane (CH 4 ) in five thermokarst lakes and three rivers in an area of widespread permafrost degradation in Northern Quebec to assess contributions from thawing permafrost and other old carbon (fixed before CE 1950) reservoirs. We compared emission pathways (dissolved gas and ebullition), seasons (summer and winter), and surface soil type (mineral and peat soils). Modern carbon (fixed after CE 1950) was the dominant source of DOC, DIC, and CH 4 of non‐peatland aquatic systems, while POC and sediment carbon were predominantly fixed in the last millennia. In the peatland systems, modern and permafrost carbon were important sources of DOC, lake DIC, lake ebullition CO 2 , and lake dissolved CH 4 . In contrast, POC, lake ebullition CH 4 , and river DIC were dominated by millennial‐old carbon. In winter, the 14 C age of DOC, DIC, and POC in the peatland lakes increased, but the 14 C age of dissolved CH 4 did not change. Our results point to a clearly older overall carbon source for ebullition CH 4 relative to dissolved CH 4 in the peatland lakes but not the non‐peatland lakes. The younger ages of dissolved CH 4 and DIC relative to DOC and POC in all lakes suggest that recent primary productivity strongly influences the large total lake CH 4 and CO 2 emissions in this area, as diffusion fluxes greatly exceed ebullition fluxes.